1. Field of the Invention
The present invention relates to apparatus and methods for removal of heat from electronic devices. In particular, the present invention relates to the attachment of heat dissipation devices to microelectronic substrates with metal balls.
2. State of the Art
Higher performance, lower cost, increased miniaturization of integrated circuit components, and greater packaging densities of integrated circuits are ongoing goals of the computer industry. As these goals are achieved, microelectronic dice become smaller. Accordingly, the density of power consumption of the integrated circuit components in the microelectronic die has increased, which, in turn, increases the average junction temperature of the microelectronic die. If the temperature of the microelectronic die becomes too high, the integrated circuits of the microelectronic die may be damaged or destroyed.
Various apparatus and techniques have been used and are presently being used for removing heat from microelectronic dice. One such heat dissipation technique involves the attachment of an integrated heat spreader to a microelectronic die. FIG. 10 illustrates an assembly 200 comprising a microelectronic die 202 (illustrated as a flip chip) physically and electrically attached to a substrate 204 (such as an interposer, a motherboard, or the like) by a plurality of solder balls 206 extending between pads 208 on an active surface 212 of the microelectronic die 202 and lands 214 on the substrate 204. To mechanically and physically reinforce the solder balls 206 connecting the microelectronic die pads 208 and the substrate lands 214, an underfill material 210 is disposed therebetween.
The assembly 200 further includes an integrated heat spreader 216 comprising a conductive plate 218 having at least one stand-off 222. The integrated heat spreader 216 is attached to a surface 224 of the substrate 204 by an adhesive layer 226 (generally a non-conductive polymer) between the substrate surface 224 and the stand-off 222, which provides mechanical strength to the assembly 200. The stand-off 222 is used to clear the height of the microelectronic die 202.
A back surface 232 of the microelectronic die 202 is in thermal contact with a first surface 228 of the integrated heat spreader conductive plate 218. A thermal interface material 234 may be disposed between the microelectronic die back surface 232 and the integrated heat spreader conductive plate first surface 228 to enhance conductive heat transfer therebetween.
The integrated heat spreader 216 is usually constructed from a thermally conductive material, such as copper, copper alloys, aluminum, aluminum alloys, and the like. The heat generated by the microelectronic die 202 is drawn into the integrated heat spreader 216 by conductive heat transfer. It is, of course, understood that additional heat dissipation devices can be attached to a second surface 238 of the integrated heat spreader conductive plate 218. These additional heat dissipation devices may include heat slugs and high surface area (finned) heat sinks, and may further include fans attached thereto, as will be evident to those skilled in the art.
One disadvantage of the assembly 200 is that the fabrication of the stand-off(s) 222 adds substantially to the cost of the assembly 200. Therefore, it would be advantageous to develop heat dissipation device designs, which achieve a lower cost and greater ease of manufacturing.